1. Field of the Invention
The invention relates to a pressure vessel for a nuclear power plant. More particularly, the invention concerns pressure vessels of reinforced concrete of special design to house the various components of a nuclear power plant such as a gas cooled high temperature reactor, gas turbine assembly and heat exchange apparatus. The pressure vessel is generally of a cylindrical configuration at least over a substantial partial area. A cavity for the high temperature reactor and a horizontally extending tunnel for the gas turbine assembly are provided in the pressure vessel. Similarly, a plurality of recesses or cavities for the components of the heat exchanger apparatus extending in the longitudinal direction through the reinforced concrete pressure vessel are also provided.
2. Background of the Prior Art
It is known that any nuclear reactor, regardless of its type must be surrounded by a container impermeable to harmful radiation for the purpose of shielding the outside against the radiation produced by nuclear fission in the core of the reactor. Furthermore, reactors operating in an overpressurized state, i.e. reactors wherein cooling is effected by means of an overpressurized cooling medium (mostly in the gaseous state) must be included in a completely impermeable and pressure resistant sheathing. This sheathing is the so-called pressure vessel. It is well known in the art to combine the radiation shield and the pressure vessel into a single tight and pressure resistant containment, performing both the functions of biological protection against radiation and the complete sealing of the nuclear reactor. This shield also acts to safely contain the internal overpressure. The known pressure vessel is made of concrete, wherein essentially inwardly directed prestresses are created in order to increase the compressive strength and impermeability by means of prestressing elements. The prestresses are greater than the stresses generated by the overpressure of the cooling medium within the reactor.
In the so called integrated nuclear reactor installations, in addition to the nuclear reactor, the heat exchanger apparatus comprising steam generators and after-heat removal systems are also arranged within the reinforced concrete pressure vessel. They may be housed in a common cavity together with the nuclear reactor. One example of a known design of this type is the THTR-300 MWe power station.
In a preferred prior art design, the nuclear reactor is installed in a cavity located in the center area of the pressure vessel and the heat exchanger components are housed in recesses, so called pods, extending in the longitudinal direction through the walls of the pressure vessel. The pods are arranged in a circular manner around the cavity of the reactor. Reinforced concrete pressure vessels of this type are described in West German Offenlegungsschrift Nos. 15 39 887 and 16 84 651.
Another known type of reinforced concrete pressure vessel for nuclear power plants houses a gas cooled high temperature reactor and one or more heat utility circuits comprising a gas turbine assembly and various heat exchanger devices. The heat exchanger devices such as recuperators, precoolers and possibly intermediate coolers are arranged in the above-described recesses or pods, while the gas turbine assembly is installed in a horizontal tunnel underneath the core of the reactor. West German Offenlegungsschrift No. 25 18 357 represents a reinforced concrete pressure vessel of this type.
In all of the above-described reinforced concrete pressure vessels the cavity for the nuclear reactor is a configuration adapted to the nuclear reactor (i.e. it has a circular cross section) and is arranged centrally in the pressure vessel. The reactor cavity diameter, together with the diameters of the recesses or pods determines the dimensions of the reinforced concrete pressure vessel. However, the width of the concrete web that must be provided between the cavity and the recesses and between the recesses and the external jacket of the pressure vessel, also plays a significant role. The dimensions of the reinforced concrete pressure vessel is thus decisively determined by the arrangement of the cavities in the pressure vessel with respect to each other. In the case of integrated nuclear power installations, the construction of the pressure vessel itself represents a very expensive structural section and requires an extended construction time. It is, therefore, desirable to design a compact structural configuration of a nuclear power plant with a favorable distribution of the individual cavities within the volume of the pressure vessel.